Extensive Polyculture Research Articles

Optimizaton quality of Agar Gracilaria verrucosa Seaweed with different density in extensive polyculture system

Optimizaton quality of Agar Gracilaria verrucosa Seaweed with different density in extensive polyculture system

Quality of Gracilaria verrucosa (Hudson) Papenf. (Rhodophyta) Seaweed with Polyculture System

An important factor in the cultivation of <i>Gracilaria verrucosa</i> seaweed in extensive polyculture ponds is (i) the determination of the right density of polyculture commodities (ii) the provision of fertilizers as nutrients to support the life of seaweed and (iii) maintenance of the pond soil as a reservoir of nutrients and to maintain the stability of the pond during the cultivation process. These important factors are indicators of success in polyculture activities of extensive ponds in producing optimal quality agar rendement, viscosity, and gel strength. This research was conducted at ponds using a Completely Randomized Design (CRD) of 3 treatments and 3 replicates; treatment A (best density + no vermicompost fertilizer + pond soil substrate), B (best density + vermicompost fertilizer + pond soil substrate), and C (best density + vermicompost fertilizer + no pond soil substrate). The treatments in this study had a significant effect on growth, number of cells, carbon content, and quality of agar viscosity of seaweed <i>G. verrucosa</i> in extensive ponds with polyculture systems.

Typology and sustainability assessment of rabbit farms in the urban and peri-urban areas of Southern Benin (West Africa)

<p>Analysis of production systems allows scientists to identify their weaknesses, particularly concerning production practices which require improvements at economic, social, and environmental levels. The present study aimed to characterise rabbit farms in the urban and peri-urban areas of South Benin and assess their sustainability using the DIAMOND method, a multicriteria sustainability assessment tool. Ninety-eight farmers were surveyed and individually interviewed. Categorical principal component and twostep cluster analyses were performed on information collected for a typology of farms. Sustainability scores were generated using the scoring scale of the DIAMOND tool. Five types of rabbit farms were identified as follows: modern extensive polyculture, traditional extensive monoculture, modern extensive monoculture, semi-intensive polyculture, and traditional extensive polyculture. Overall, all the rabbit farms had good scores for the economic sustainability pillar but were socially limited. They were all similar in their economic and environmental performances. In particular, semi-intensive farms were the most socially sustainable, whereas traditional farms (either in polyculture or monoculture) showed the lowest social performances. Furthermore, there were significant differences between farms for criteria relating to consumers’ demands and resource use. Semi-intensive farms responded best to consumers’ demands, whereas the traditional polyculture farm type was the most resource use efficient. Overall, in the urban and peri-urban areas of South Benin, the most sustainable rabbit farms were semi-intensive. Irrespective of farm type, positive coefficients of correlations were recorded among the three pillars of sustainability, being significant between the social and economic pillars on one hand, and between the social and environmental pillars on the other hand. These results suggest that efforts to improve farm social performance would also positively affect their economic and environmental performances and improve overall farm sustainability.</p>

Growth performance of Jayanti Rohu and Amur Common carp in extensive polyculture system

Growth performance of Jayanti Rohu and Amur Common carp in extensive polyculture system

LCA and emergy accounting of aquaculture systems: Towards ecological intensification

An integrated approach is required to optimise fish farming systems by maximising output while minimising their negative environmental impacts. We developed a holistic approach to assess the environmental performances by combining two methods based on energetic and physical flow analysis. Life Cycle Assessment (LCA) is a normalised method that estimates resource use and potential impacts throughout a product's life cycle. Emergy Accounting (EA) refers the amount of energy directly or indirectly required by a product or a service. The combination of these two methods was used to evaluate the environmental impacts of three contrasting fish-farming systems: a farm producing salmon in a recirculating system (RSF), a semi-extensive polyculture pond (PF1) and an extensive polyculture pond (PF2). The RSF system, with a low feed-conversion ratio (FCR = 0.95), had lower environmental impacts per tonne of live fish produced than did the two pond farms, when the effects on climate change, acidification, total cumulative energy demand, land competition and water dependence were considered. However, RSF was clearly disconnected from the surrounding environment and depended highly on external resources (e.g. nutrients, energy). Ponds adequately incorporated renewable natural resources but had higher environmental impacts due to incomplete use of external inputs. This study highlighted key factors necessary for the successful ecological intensification of fish farming, i.e., minimise external inputs, lower the FCR, and increase the use of renewable resources from the surrounding environment. The combination of LCA and EA seems to be a practical approach to address the complexity of optimising biophysical efficiency in aquaculture systems.

Sustainability and Local People’s Participation in Coastal Aquaculture: Regional Differences and Historical Experiences in Sri Lanka and the Philippines

This article discusses environmental sustainability in aquaculture and its contribution to poverty alleviation, based on field studies in Sri Lanka and the Philippines. The aquaculture practices studied are the monoculture of the black tiger prawn (Penneaus monodon) and milkfish (Chanos chanos) and the polyculture of the two species together with the mud crab (Scylla serrata). Factors affecting economic viability, social equity and environmental impacts in aquaculture are discussed and used to illuminate local and regional differences between aquaculture in Sri Lanka and the Philippines. Findings indicate that the most significant difference is the level of participation by local people (i.e., people originating < or =10 km away from the farm location). In the Philippines, 84 % of the people involved in aquaculture are locals, whereas in Sri Lanka, 55% are outsiders. Whether differences between the two areas can be explained by analyzing regional conditions, which might have resulted in different aquaculture practices, is discussed. In Sri Lanka, semi-intensive shrimp monoculture is currently the most common practice, whereas in the Philippines, extensive shrimp/fish polyculture is more common. Previous studies, as well as fieldwork, indicate that extensive culture practices reduce environmental impacts and benefit local people more. Sustainability in aquaculture is, however, also dependent on the extent of mangrove conversion into ponds. As such, extensive and locally owned farms do not necessarily result in an all but sustainable situation. Keeping this in mind, it is discussed if extensive polyculture practices might result in a more sustainable aquaculture, both environmentally and socioeconomically.

AN EMPIRICAL TYPOLOGY OF BRACKISH-WATER POND AQUACULTURE SYSTEMS IN THE PHILIPPINES: A TOOL TO AID COMPARATIVE STUDY IN THE SECTOR

Aquaculture in the Philippines is long-established but has witnessed rapid technical change in the last 20 years with the introduction of hatchery technology and commercial feed mills changing the production possibilities for a fishpond operator. To understand the sector, a typology of brackish-water pond farming systems is constructed using multivariate methods (principal components analysis, cluster analysis). Eight input variables across all major factors of production are used in the analysis, gathered from a net sample of 136 farms in two regions in 2003. Three latent variables are described, accounting for 58% of variance in the original data: specialization; land vs. labor intensity; and feeding intensity. Five clusters (farm types) are subsequently described: extensive polyculture (40% of sample); semi-intensive prawn-oriented polyculture (11%); low-input labor-intensive farms (27%); very large, extensive milkfish-oriented farms (8%); and semi-intensive milkfish monoculture farms (14%). Implications for technical efficiency estimation and comparative study of economic indicators are discussed.

Integrated aquaculture: rationale, evolution and state of the art emphasizing seaweed biofiltration in modern mariculture

Rising global demand for seafood and declining catches have resulted in the volume of mariculture doubling each decade, a growth expected by the FAO to persist in the decades to come. This growth should use technologies with economical and environmental sustainability. Feed accounts for about half the cost in current high-volume fed mono-species aquaculture, mainly fish net pens or shrimp/fish ponds, yet most of this feed becomes waste. The resulting environmental impact and rising feed costs therefore hamper further growth of such farms. As in certain traditional polyculture schemes, plants can drastically reduce feed use and environmental impact of industrialized mariculture and at the same time add to its income. These nutrient-assimilating photoautotrophic plants use solar energy to turn nutrient-rich effluents into profitable resources. Plants counteract the environmental effects of the heterotrophic fed fish and shrimp and restore water quality. Today's integrated intensive aquaculture approaches, developed from traditional extensive polyculture, integrate the culture of fish or shrimp with vegetables, microalgae, shellfish and/or seaweeds. Integrated mariculture can take place in coastal waters or in ponds and can be highly intensified. Today's technologies are well studied and documented. They are generic, modular and adaptable for several culture combinations of fish, shrimp, shellfish, abalone, sea urchin and several species of commercially important seaweeds and vegetables. A 1-ha land-based integrated seabream–shellfish–seaweed farm can produce 25 tons of fish, 50 tons of bivalves and 30 tons fresh weight of seaweeds annually. Another farm model can produce in 1 ha 55 tons of seabream or 92 tons of salmon, with 385 or 500 fresh weight of seaweed, respectively, without pollution. Preliminary calculations show a potential for high profitability with large integrated farms. Several freshwater integrated fish–vegetable farms and a couple of modern fish–algae–shellfish/abalone integrated mariculture farms exist today, and several additional farms are planned. Three major international R&D projects promise to soon expand the horizons of the technology further. Therefore, modern integrated systems in general, and seaweed-based systems in particular, are bound to play a major role in the sustainable expansion of world aquaculture.

Mathematical modelling to assess the carrying capacity for multi-species culture within coastal waters

Abstract In the context of aquaculture, carrying capacity is generally understood as the standing stock of a particular species at which production is maximised without negatively affecting growth rates. The estimation of carrying capacity for aquaculture is a complex issue. That complexity stems from the many interactions between and among cultivated and non-cultivated species, as well as between those species and their physical and chemical environments. Mathematical models may help to resolve these interactions, by analysing them in a dynamic manner. Previous carrying capacity models have considered the biogeochemical processes that influence growth of cultivated species in great detail. However, physical processes tend to have been addressed very simplistically. Further, most modelling has been for monocultures, despite the increasing importance of multi-species (=polyculture) systems. We present here a two-dimensional coupled physical–biogeochemical model implemented for Sungo Bay, Shandong Province, People’s Republic of China. Sungo Bay is used for extensive polyculture, where bivalve shellfish and kelp are the most important cultivated species. Data collected over 13 years (1983–2000) was available for modelling. Our main objectives were to implement the model, achieving reasonable calibration and validation with independent data sets, for use in estimating the environmental carrying capacity for polyculture of scallops and oysters. Findings indicate that the model successfully reproduces some of the main features of the simulated system. Although requiring some further work to improve predictive capability in parts, predictions clearly indicate that Sungo Bay is being exploited close to the environmental carrying capacity for suspension-feeding shellfish. Comparison of different culture scenarios also indicates that any significant increase in yield will depend largely on a more optimal spatial distribution of the different cultivated species.

Profitability and technical efficiency of aquaculture systems in pampaanga, philippines

We evaluate the profitability and technical efficiency of aquaculture in the Philippines. Farm‐level data are used to compare two production systems corresponding to the intensive monoculture of tilapia in freshwater ponds and the extensive polyculture of shrimps and fish in brackish water ponds. Both activities are very lucrative, with brackish water aquaculture achieving the higher level of profit per farm. Stochastic frontier production functions reveal that technical efficiency is low in brackish water aquaculture, with a mean of 53%, explained primarily by the operator's experience and by the frequency of his visits to the farm. In freshwater aquaculture, the farms achieve a mean efficiency level of 83%. The results suggest that the provision of extension services to brackish water fish farms might be a cost‐effective way of increasing production and productivity in that sector. By contrast, technological change will have to be the driving force of future productivity growth in freshwater aquaculture.

Socio-economic impacts of shrimp culture

Farmed shrimp contributed 27% of total world shrimp production in 1995 with a volume of 712 000 tonnes. Undoubtedly, the shrimp culture industry earns valuable foreign exchange for developing countries and generates jobs across the industry from fry gatherers to growers and processors. However, grave socio-economic consequences – including conversion, expropriation and privatization of mangroves and other lands; salinization of water and soil; decline in food security; marginalization of coastal communities, unemployment and urban migration; and social conflicts – have followed in the wake of, shrimp farm development in the Philippines and other tropical countries. The paper focuses on mangrove ecosystems: the valuation and cost-benefit analysis of their goods and services, and the mangrove-offshore fisheries connection. Research gaps in these areas and the need to internalize the ecological and socio-economic costs (‘externalities’) of shrimp farming are highlighted. Other recommendations include mangrove conservation and rehabilitation, enforcement of existing legislation, and introduction of environment-friendly aquaculture within the broader framework of community-based, integrated coastal area management, e.g. the traditional, extensive polyculture ponds in Indonesia.